1. Core Kubelet changes to implement In-place Pod Vertical Scaling.
2. E2E tests for In-place Pod Vertical Scaling.
3. Refactor kubelet code and add missing tests (Derek's kubelet review)
4. Add a new hash over container fields without Resources field to allow feature gate toggling without restarting containers not using the feature.
5. Fix corner-case where resize A->B->A gets ignored
6. Add cgroup v2 support to pod resize E2E test.
KEP: /enhancements/keps/sig-node/1287-in-place-update-pod-resources
Co-authored-by: Chen Wang <Chen.Wang1@ibm.com>
Currently, there are some unit tests that are failing on Windows due to
various reasons:
- config options not supported on Windows.
- files not closed, which means that they cannot be removed / renamed.
- paths not properly joined (filepath.Join should be used).
- time.Now() is not as precise on Windows, which means that 2
consecutive calls may return the same timestamp.
- different error messages on Windows.
- files have \r\n line endings on Windows.
- /tmp directory being used, which might not exist on Windows. Instead,
the OS-specific Temp directory should be used.
- the default value for Kubelet's EvictionHard field was containing
OS-specific fields. This is now moved, the field is now set during
Kubelet's initialization, after the config file is read.
Track how long it takes for pod updates to propagate from detection
to successful change on API server. Will guide future improvements
in pod start and shutdown latency.
Metric is `kubelet_pod_status_sync_duration_seconds` and is ALPHA
stability. Histogram buckets are chosen based on distribution of
observed status delays in practice.
- PreemptionByKubeScheduler (Pod preempted by kube-scheduler)
- DeletionByTaintManager (Pod deleted by taint manager due to NoExecute taint)
- EvictionByEvictionAPI (Pod evicted by Eviction API)
- DeletionByPodGC (an orphaned Pod deleted by PodGC)PreemptedByScheduler (Pod preempted by kube-scheduler)
Terminal pods may continue to report a ready condition of true because
there is a delay in reconciling the ready condition of the containers
from the runtime with the pod status. It should be invalid for kubelet
to report a terminal phase with a true ready condition. To fix the
issue, explicitly override the ready condition to false for terminal
pods during status updates.
Signed-off-by: David Porter <david@porter.me>
Create an E2E test that creates a job that spawns a pod that should
succeed. The job reserves a fixed amount of CPU and has a large number
of completions and parallelism. Use to repro github.com/kubernetes/kubernetes/issues/106884
Signed-off-by: David Porter <david@porter.me>
Other components must know when the Kubelet has released critical
resources for terminal pods. Do not set the phase in the apiserver
to terminal until all containers are stopped and cannot restart.
As a consequence of this change, the Kubelet must explicitly transition
a terminal pod to the terminating state in the pod worker which is
handled by returning a new isTerminal boolean from syncPod.
Finally, if a pod with init containers hasn't been initialized yet,
don't default container statuses or not yet attempted init containers
to the unknown failure state.
In the following code pattern, the log message will get logged with v=0 in JSON
output although conceptually it has a higher verbosity:
if klog.V(5).Enabled() {
klog.Info("hello world")
}
Having the actual verbosity in the JSON output is relevant, for example for
filtering out only the important info messages. The solution is to use
klog.V(5).Info or something similar.
Whether the outer if is necessary at all depends on how complex the parameters
are. The return value of klog.V can be captured in a variable and be used
multiple times to avoid the overhead for that function call and to avoid
repeating the verbosity level.
A number of race conditions exist when pods are terminated early in
their lifecycle because components in the kubelet need to know "no
running containers" or "containers can't be started from now on" but
were relying on outdated state.
Only the pod worker knows whether containers are being started for
a given pod, which is required to know when a pod is "terminated"
(no running containers, none coming). Move that responsibility and
podKiller function into the pod workers, and have everything that
was killing the pod go into the UpdatePod loop. Split syncPod into
three phases - setup, terminate containers, and cleanup pod - and
have transitions between those methods be visible to other
components. After this change, to kill a pod you tell the pod worker
to UpdatePod({UpdateType: SyncPodKill, Pod: pod}).
Several places in the kubelet were incorrect about whether they
were handling terminating (should stop running, might have
containers) or terminated (no running containers) pods. The pod worker
exposes methods that allow other loops to know when to set up or tear
down resources based on the state of the pod - these methods remove
the possibility of race conditions by ensuring a single component is
responsible for knowing each pod's allowed state and other components
simply delegate to checking whether they are in the window by UID.
Removing containers now no longer blocks final pod deletion in the
API server and are handled as background cleanup. Node shutdown
no longer marks pods as failed as they can be restarted in the
next step.
See https://docs.google.com/document/d/1Pic5TPntdJnYfIpBeZndDelM-AbS4FN9H2GTLFhoJ04/edit# for details
Most of these could have been refactored automatically but it wouldn't
have been uglier. The unsophisticated tooling left lots of unnecessary
struct -> pointer -> struct transitions.
The status manager syncBatch() method processes the current state
of the cache, which should include all entries in the channel. Flush
the channel before we call a batch to avoid unnecessary work and
to unblock pod workers when the node is congested.
Discovered while investigating long shutdown intervals on the node
where the status channel stayed full for tens of seconds.
Add a for loop around the select statement to avoid unnecessary
invocations of the wait.Forever closure each time.
The kubelet must not allow a container that was reported failed in a
restartPolicy=Never pod to be reported to the apiserver as success.
If a client deletes a restartPolicy=Never pod, the dispatchWork and
status manager race to update the container status. When dispatchWork
(specifically podIsTerminated) returns true, it means all containers
are stopped, which means status in the container is accurate. However,
the TerminatePod method then clears this status. This results in a
pod that has been reported with status.phase=Failed getting reset to
status.phase.Succeeded, which is a violation of the guarantees around
terminal phase.
Ensure the Kubelet never reports that a container succeeded when it
hasn't run or been executed by guarding the terminate pod loop from
ever reporting 0 in the absence of container status.
In an e2e run, out of 1857 pod status updates executed by the
Kubelet 453 (25%) were no-ops - they only contained the UID of
the pod and no status changes. If the patch is a no-op we can
avoid invoking the server and continue.
The types were different so the diff output is not useful, both
should be pointers:
```
Feb 05 19:44:40 ci-ln-6k7l4-w-c-w9wbb.c.openshift-gce-devel-ci.internal hyperkube[2737]: I0205 19:44:40.222259 2737 status_manager.go:642] Pod status is inconsistent with cached status for pod "prometheus-k8s-1_openshift-monitoring(0e9137b8-3bd2-4353-b7f5-672749106dc1)", a reconciliation should be triggered:
Feb 05 19:44:40 ci-ln-6k7l4-w-c-w9wbb.c.openshift-gce-devel-ci.internal hyperkube[2737]: interface{}(
Feb 05 19:44:40 ci-ln-6k7l4-w-c-w9wbb.c.openshift-gce-devel-ci.internal hyperkube[2737]: - s"&PodStatus{Phase:Running,Conditions:[]PodCondition{PodCondition{Type:Initialized,Status:True,LastProbeTime:0001-01-01 00:00:00 +0000 UTC,LastTransitionTime:2020-02-05 19:13:30 +0000 UTC,Reason:,Message:,},PodCondit>
Feb 05 19:44:40 ci-ln-6k7l4-w-c-w9wbb.c.openshift-gce-devel-ci.internal hyperkube[2737]: + v1.PodStatus{
Feb 05 19:44:40 ci-ln-6k7l4-w-c-w9wbb.c.openshift-gce-devel-ci.internal hyperkube[2737]: + Phase: "Running",
Feb 05 19:44:40 ci-ln-6k7l4-w-c-w9wbb.c.openshift-gce-devel-ci.internal hyperkube[2737]: + Conditions: []v1.PodCondition{
```
